(1) Field of the Invention
This invention relates to an apparatus for controlling an opening angle (or position) of a throttle valve on complete firing in an internal combustion engine, and particularly to an apparatus for controlling the opening angle of a throttle valve on complete firing until the internal combustion engine has shifted to a situation of warming up after the engine started and the complete firing was sensed.
(2) Description of the Prior Art
Heretofore, it has been proposed to provide a carburetor comprising a throttle valve disposed in an intake barrel of the carburetor, a choke valve disposed on the upstream side thereof, a motor driving said valves, and means for detecting the temperature and rotational speed of the engine, the opening angles of the throttle valve and the choke valve being appropriately established and controlled in response to temperature at the time of starting and warming up the engine (for example, see Japanese Patent Application No. 38165/1982.
An example for controlling opening angles of a throttle valve and a choke valve in such carburetors is illustrated in FIG. 1 wherein time is plotted as the abscissa and opening angles of the throttle valve and the choke valve as the ordinate, in which line SV designates the throttle valve and line CV designates the choke valve.
As is apparent from FIG. 1, two valves are held at their starting positions (starting opening angles), more specifically, the throttle valve and the choke valve are maintained at substantially full opened position Th 1 and substantially full closed position, respectively, immediately after turning on a starter switch of the engine at time T0.
Then, when complete firing of the engine is sensed at time T1, both the valves are moved quickly to warming-up positions (the choke valve CV is rushed to substantially full opened position TH1, while the throttle valve SV is rushed to position Th 3 which has previously been fixed in response to temperatures of the engine) at time T2 after the elapse of a predetermined delay time from the time T1.
In such a method for controlling opening angles of a throttle valve and a choke valve in conventional carburetors, when the engine reaches its complete firing state, the throttle valve is rapidly closed, while the choke valve is rapidly fully opened, so that the air fuel ratio of the mixture decreases suddenly.
For this reason, explosion energy of the engine decreases sharply, and in addition the relieving effect of the choke valve becomes temporarily excessive. Thus, conventional carburetors have the disadvantage that the engine is liable to stall in case of the complete firing.
As a countermeasure for the disadvantage mentioned above, it may be considered that each rate of change in both the valves is moderated (for example, the period of time required for decreasing the opening angle of the throttle valve from position Th 1 to position Th 3 is prolonged).
In case of a controlling method such as described above, however, the air fuel ratio of the mixture becomes excessive, and plugs are apt to be wetted so that the disadvantage remains that the engine is apt to stall on the complete firing.